In the related art, a cathode electrode of an organic light emitting device, an organic solar cell, or the like basically uses indium tin oxide (ITO) as a primary electrode and primarily uses a secondary electrode made of metal in order to prevent loss of optical efficiency by high resistance of the ITO, and the like.
In a method for forming the secondary electrode, the secondary electrode may be formed by depositing and patterning metal on ITO which is fully deposited on a substrate, passivating metal again or forming the secondary electrode at a groove portion of a substrate with a groove, and thereafter, depositing the ITO as the primary electrode thereon. However, this method is not a reasonable method because the number of processes is many and an increase in price of a substrate occurs.